Synchronicity and Cooperativity

More support for Jung's Collective Unconscious

Recent studies examined group dynamics among known intimates and random strangers. Perceptions and cooperativity were tested along with individual physiological parameters, such as heart rate and EEG brain wave patterns. Surprisingly, synchronicity amongst the individuals evolved with cooperativity.

Shared Arousal

The fascinating phenomenon of physiological synchrony intrigues researchers seeking to understand how human brains and bodies coordinate during social interactions. Looking at heart rate synchrony may turn out to be reliable measure for assessing team dynamics.

Significance Groups can outperform individuals in problem-solving, but failure to critically reexamine ideas may lead to suboptimal outcomes as in groupthink. Prior work has shown similar patterns of brain activity between individuals holding shared perspectives. Whether interpersonal heart rate synchrony, a peripheral index of shared arousal, can predict the outcome of group discussions remains unknown. We address this gap by collecting heart rate data from groups performing a discussion task that required critical examination of all available information to override inferior, default options. We found heart rate synchrony predicted the probability that groups would reach the correct consensus with >70% cross-validation accuracy, thus, providing a biomarker of interpersonal engagement that facilitates adaptive learning and effective information sharing during collective decision-making.

Abstract Groups often outperform individuals in problem-solving. Nevertheless, failure to critically evaluate ideas risks suboptimal outcomes through so-called groupthink. Prior studies have shown that people who hold shared goals, perspectives, or understanding of the environment show similar patterns of brain activity, which itself can be enhanced by consensus-building discussions. Whether shared arousal alone can predict collective decision-making outcomes, however, remains unknown. To address this gap, we computed interpersonal heart rate synchrony, a peripheral index of shared arousal associated with joint attention, empathic accuracy, and group cohesion, in 44 groups (n = 204) performing a collective decision-making task. The task required critical examination of all available information to override inferior, default options and make the right choice. Using multidimensional recurrence quantification analysis (MdRQA) and machine learning, we found that heart rate synchrony predicted the probability of groups reaching the correct consensus decision with >70% cross-validation accuracy–significantly higher than that predicted by the duration of discussions, subjective assessment of team function or baseline heart rates alone. We propose that heart rate synchrony during group discussion provides a biomarker of interpersonal engagement that facilitates adaptive learning and effective information sharing during collective decision-making. -KM Sharika, et al.

Hmmmm …. I wonder if trial juries will now be followed by hacking their fitbit monitors?

Shared perspective leads to brain synchrony

Experimental design and analyses. A: Participants watched the same movie clip twice, once from the detective and another time from the interior decorator perspective, with the starting perspective counterbalanced across participants. B: Mantel test was used to compare the pairwise ISC values (upper triangle entries) to a correlation matrix template (lower triangle entries) where ISC in same-perspective pairs (red) was higher than different-perspective pairs (blue). C: Subjects were classified according to the labels of the training subjects (detective — red, decorator — blue) with whom their ISC was highest. Proximity between two dots reflects the strength of the ISC between those subjects. The nearest three neighbors are indexed according to their proximity to the current subject, and the links are highlighted with the color corresponding to their class. For k = 3 the current subject (white dot) would be classified as a detective because two of the three nearest neighbors (neighbors 2 and 3) are detectives.

For successful communication, we need to understand the external world consistently with others. This task requires sufficiently similar cognitive schemas or psychological perspectives that act as filters to guide the selection, interpretation and storage of sensory information, perceptual objects and events. Here we show that when individuals adopt a similar psychological perspective during natural viewing, their brain activity becomes synchronized in specific brain regions. We measured brain activity with functional magnetic resonance imaging (fMRI) from 33 healthy participants who viewed a 10-min movie twice, assuming once a ‘social’ (detective) and once a ‘non-social’ (interior decorator) perspective to the movie events. Pearson's correlation coefficient was used to derive multisubject voxelwise similarity measures (inter-subject correlations; ISCs) of functional MRI data. We used k-nearest-neighbor and support vector machine classifiers as well as a Mantel test on the ISC matrices to reveal brain areas wherein ISC predicted the participants' current perspective. ISC was stronger in several brain regions—most robustly in the parahippocampal gyrus, posterior parietal cortex and lateral occipital cortex—when the participants viewed the movie with similar rather than different perspectives. Synchronization was not explained by differences in visual sampling of the movies, as estimated by eye gaze. We propose that synchronous brain activity across individuals adopting similar psychological perspectives could be an important neural mechanism supporting shared understanding of the environment. - JM Lahnakoski, et al.

Theta waves for mimicked movement

Previous research revealed that pairs with strong social ties (romantic partners) display greater EEG gamma bands (30–60 Hz) synchronization when gazing at each other and expressing positive emotion in naturalistic conversation when compared to pairs with weaker social ties (strangers); this finding is not found in theta (4-7 Hz), alpha (8-12 Hz), or beta (13-30 Hz) bands. Thus, emotional engagement in pairs with higher levels of intimacy induces greater EEG gamma synchronization. This gamma oscillation is also related to social cognition, such as empathy, mentalization, and emotion.

In a recent experiment, researchers examined the differences in interpersonal neural network topology between stranger and acquaintance pairs when tasked with joint-tapping. They found large positive correlation between local and global efficiency in the theta band as well as other bands. Thus, the stranger pairs integrated information more efficiently in the intra-/inter-brain network than the acquaintance pairs. When participants performed contrived tasks that include joint action, their EEGs tended to converge in a lower frequency band. For example, inter-brain EEG synchronization is stronger in the theta and alpha bands during a joint task than when performing the task alone.

Experimental setups. (A) Participants sat side-by-side and wore two wireless electroencephalographs (EEG). (B) Each participant gazed at a fixation point in front of him/her during anti-phase tapping. (C) The participants performed alternative (anti-phase) tapping. (D) We conducted four different tapping conditions: slow, fast, free, and pseudo conditions. - Y Kurihara, et al.

The strategies for social interaction between strangers differ from those between acquaintances, whereas the differences in neural basis of social interaction have not been fully elucidated. In this study, we examined the geometrical properties of interpersonal neural networks in pairs of strangers and acquaintances during antiphase joint tapping. Dual electroencephalogram (EEG) of 29 channels per participant was measured from 14 strangers and 13 acquaintance pairs. Intra-brain synchronizations were calculated using the weighted phase lag index (wPLI) for intra-brain electrode combinations, and inter-brain synchronizations were calculated using the phase locking value (PLV) for inter-brain electrode combinations in the theta, alpha, and beta frequency bands. For each participant pair, electrode combinations with larger wPLI/PLV than their surrogates were defined as the edges of the neural networks. We calculated global efficiency, local efficiency, and modularity derived from graph theory for the combined intra- and inter-brain networks of each pair. In the theta band networks, stranger pairs showed larger local efficiency than acquaintance pairs, indicating that the two brains of stranger pairs were more densely connected. Hence, weak social ties require extensive social interactions and result in high efficiency of information transfer between neighbors in neural network. - Y Kurihara, et al.

Study finds that interaction between strangers leads to higher levels of inter- and intra-brain synchronization compared to that in close acquaintances. Credit: Yuto Kurihara from Waseda University

Theta inter-brain synchronization is related to motor coordination process; brain-to-brain theta synchronization depends on engagement in joint action rather than on social, emotional cognition. Social interactions with a high mental load induce higher inter-brain synchrony. Socially attentive situations necessitate more mentalization, which induce brain synchronization. Hence, cooperation between strangers may produce high mental loading and subsequently, synchrony.

But what about romance?

A recent study tested the hypothesis that co-regulation of sympathetic and behavioral rhythms between a man and a woman serves as a mechanism that promotes attraction. It highlights physiological synchrony — the alignment of physiological responses between individuals — and its impact on perceived romantic attraction.

Forty-eight men and women meet for five-minute speed dates in a dedicated room with a homey arrangement while their physiology is sampled at 4 Hz using Empatica E4 wristbands²⁸. Physiological synchrony between partners is calculated as the Pearson Correlation between the levels of electrodermal activity (EDA) of the man and the woman during the date. Participants rate their interest in the partner twice, once before they start to interact, and again after the date is complete. To assess individual rates of synchrony and attraction, participants partake in four dates, and we calculate their Individual Electrodermal Synchrony Scores and their Individual Romantic Attractiveness Scores by averaging the scores across their dates. We investigate whether initial interest affects physiological synchrony during the date and whether individual synchrony scores predict individual attractiveness scores. - M Cohen et al.

The mechanisms of romantic bonding in humans are largely unknown. Recent research suggests that physiological synchrony between partners is associated with bonding. This study combines an experimental approach with a naturalistic dating setup to test whether the individual differences in social and nonsocial synchrony are interdependent, and linked to romantic attractiveness. In a preregistered online experiment with 144 participants, we discover that inducing physiological synchrony between an actor and an actress determines their attractiveness ratings by participants, indicating that synchrony can increase perceived attraction. In a lab-based naturalistic speed-dating experiment, we quantify in 48 participants the individual tendency for social physiological synchrony, nonsocial sensorimotor synchrony, and romantic attractiveness. We discover that the individual propensity to synchronize in social and nonsocial tasks is correlated. Some individuals synchronize better regardless of partners or tasks, and such Super Synchronizers are rated as more attractive. Altogether, this demonstrates that humans prefer romantic partners who can synchronize.

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REFERENCES

KM Sharika, et al. Interpersonal heart rate synchrony predicts effective information processing in a naturalistic group decision-making task. May 16, 2024 PNAS 121 (21) e2313801121 https://doi.org/10.1073/pnas.2313801121

JM Lahnakoski, et al. Synchronous brain activity across individuals underlies shared psychological perspectives. Neuroimage. 2014 Oct 15;100(100):316-24. doi: 10.1016/j.neuroimage.2014.06.022.

Y Kurihara, et al. The topology of interpersonal neural network in weak social ties, Scientific Reports (2024). DOI: 10.1038/s41598-024-55495-7

M Cohen, et al. Social and nonsocial synchrony are interrelated and romantically attractive. Communications Psychology (2024). DOI: 10.1038/s44271-024-00109-1